The reuse of removed asphalt materials from road paving and roofing has gained greater acceptance for the past two decades. However, paved surfaces and roofing surfaces still show a finite durability, and continue to be removed. This burden of materials and demand for natural resources could be reduced by increasing the content of removed materials into the newly furnished asphalt product.
Rejuvenation throughout most of the twentieth century typically referred to a process of recoating an existing paved surface. A more durable solution is the reuse of materials such as reclaimed or recycled asphalt pavement (RAP) or recycled asphalt shingle (RAS), removed from an old road or roof then reincorporated into a new asphalt surface. State transportation agencies are often reluctant to use higher RAP or RAS content because they contain asphalt binder that has been highly aged, and is much stiffer than virgin binder. (RAS has an even stiffer binder than RAP). Accordingly, there has been a concern that incorporating higher RAP or RAS content may lead to asphalt mixtures that are high in stiffness and consequently might be susceptible to failures in the field such as cracking or moisture damage. The stiffness increase can be mitigated to some extent by the use of a softer binder, but if incomplete blending occurs between the soft binder and the much stiffer RAP/MSW/PCAS binders, the resultant mixture may still be susceptible to cracking, moisture damage, or rutting in the field.